International Patent Publication No. WO 97/02496 describes a monostatic FMCW (frequency modulated continuous wave) radar sensor for a vehicle for detecting objects, in which at least one antenna feed, in conjunction with a dielectric lens, is provided both for transmitting and for receiving a corresponding echo signal. At least one antenna feed is connected via a rat-race ring or a double rat-race ring to a ring mixer, so that it is possible to dispense with a costly circulator. This device provides for a three-channel transmitting and receiving concept, in which a separate evaluation unit is provided for each of the three channels for evaluating the received signals. In this device, an evaluation channel is permanently allocated to each receiving antenna.
European Patent No. 0733913 describes a radar module having a plurality of antennas, transmitting devices and receiving devices. The received signals are supplied via a selector to an analog-to-digital converter, the selector switching through one channel alternating in turn.